1. Field of the Invention
The present invention relates to an object shooting condition judging device, an image quality adjustment device, and an image shooting apparatus, and specifically, to an object shooting condition judging device for judging object shooting conditions such as light source types by an ultraviolet light receiving element (i.e., an ultraviolet light detecting element) as an external sensor and an image quality adjustment device for adjusting image quality based on the judged object shooting condition in an image shooting apparatus such as a digital camera and video camera, and an image shooting apparatus including the object shooting condition judging device and the image quality adjustment device.
2. Description of a Related Art
Recently, a digital camera and a portable phone equipped with a digital camera are becoming remarkably widespread. These digital cameras, differently from a silver halide film camera, often shoot an object as a subject of shooting while referring to the image of the object in real time by a liquid crystal display device, and the shot image is viewed on the scene.
Further, since the equipment is made compact and lightweight, it is desired that the processing of white balance adjustment according to the difference in light source types in the shooting location is simplified as much as possible.
Generally, in a digital camera and video camera, white balance is adjusted by auto white balance. As the auto white balance, there are the external sensor system and the image detection type. The external sensor system analyzes the color of ambient light cast on the camera, as values, by a color measuring sensor and calculates white balance gain based on the measured color values, thereby adjusting white balance.
On the other hand, the image detection type calculates white balance gain by estimating illumination light source color from the output of the imaging device, and uses RGB signals obtained from the output of the imaging device as criteria.
As the external sensor system, conventionally, a system of measuring light on the scene in four wavebands including ultraviolet light, judging the light source by comparing the ultraviolet light intensity with the light intensity of other three wavebands, and using the result as white balance compensation data has been proposed (Japanese Patent Application Laid-Open (JP-A) No. 2002-71458).
However, in the conventional technology, since the ultraviolet light intensity and the light intensity of other three wavebands are compared, the technology is complicated and quick response can not be obtained. Further, in the case where the ambient illumination light of the camera and the illumination light of the object are different, when shooting outdoors from indoors and the like is attempted, there arises a problem in that white balance can not be adjusted because some of ultraviolet light is absorbed by windowpanes.